The 20 apps are all pre-installed from factory. If you don't trust those, then you need to change your device. There is no trivial way of removing them short of rooting or flashing a new ROM.
Even factory apps ought to be given the minimum permissions needed to do their job - otherwise someone will find an exploit for one and have an easier time doing evils.
Use App Manager from f-droid and enable adb mode or wireless debugging and then freeze the unwanted apps. The manual tells you exactly how to use adb over USB or enable wireless debugging.
